How to Identify Source NAT vs Destination NAT from Session Information
This PCNSA practice question tests your understanding of core concepts. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Refer to the exhibit.
```
admin@PA-220> show session id 12345
Session ID: 12345
Application: ssl
Source IP: 10.1.1.100
Destination IP: 172.16.1.10
Source Port: 45012
Destination Port: 443
Source Zone: trust
Destination Zone: dmz
Ingress Interface: ethernet1/1
Egress Interface: ethernet1/2
NAT: source (10.1.1.100 -> 192.168.1.100)
State: active
--------------------------------------------------------------------------
```
Refer to the exhibit. Based on the session information, which type of NAT is being performed?
Exhibit
Refer to the exhibit.
```
admin@PA-220> show session id 12345
Session ID: 12345
Application: ssl
Source IP: 10.1.1.100
Destination IP: 172.16.1.10
Source Port: 45012
Destination Port: 443
Source Zone: trust
Destination Zone: dmz
Ingress Interface: ethernet1/1
Egress Interface: ethernet1/2
NAT: source (10.1.1.100 -> 192.168.1.100)
State: active
--------------------------------------------------------------------------
```
A
No NAT is being performed
Why wrong: The exhibit shows a translation from 10.1.1.100 to 192.168.1.100, so NAT is active.
B
Source NAT
The source address is translated from 10.1.1.100 to 192.168.1.100, which is source NAT.
C
Port Address Translation (PAT)
Why wrong: PAT implies source port translation; no port change is visible in the exhibit.
D
Destination NAT
Why wrong: Destination NAT would change the destination IP, which is not shown here.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Source NAT
The session information shows the source IP address being translated from a private IP (e.g., 10.0.0.1) to a public IP (e.g., 203.0.113.1), which is characteristic of Source NAT (SNAT). Destination NAT (D) would change the destination IP, not the source. Port Address Translation (C) is a form of SNAT that also translates port numbers, but the question asks for the type of NAT, and based on the source IP change, the answer is Source NAT. No NAT (A) would leave the source IP unchanged, which is not the case.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
No NAT is being performed
Why it's wrong here
The exhibit shows a translation from 10.1.1.100 to 192.168.1.100, so NAT is active.
✓
Source NAT
Why this is correct
The source address is translated from 10.1.1.100 to 192.168.1.100, which is source NAT.
Related concept
Static NAT maps one inside address to one outside address.
✗
Port Address Translation (PAT)
Why it's wrong here
PAT implies source port translation; no port change is visible in the exhibit.
✗
Destination NAT
Why it's wrong here
Destination NAT would change the destination IP, which is not shown here.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Command / output trap
The exhibit shows a translation from 10.1.1.100 to 192.168.1.100, so NAT is active.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCNSA NAT questions on configuration and troubleshooting.
Core Concepts — This question tests Core Concepts — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Source NAT — The session information shows the source IP address being translated from a private IP (e.g., 10.0.0.1) to a public IP (e.g., 203.0.113.1), which is characteristic of Source NAT (SNAT). Destination NAT (D) would change the destination IP, not the source. Port Address Translation (C) is a form of SNAT that also translates port numbers, but the question asks for the type of NAT, and based on the source IP change, the answer is Source NAT. No NAT (A) would leave the source IP unchanged, which is not the case.
What should I do if I get this PCNSA question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCNSA NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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